In particular, the invention relates to a pulse transformer with a high-current loop extension of a secondary coil according to German Patent Application P 44 23 992.0. Optionally, the high-current loop extension is exchangeable. This patent application proposes to allow a high-current conductor to act upon a magnetic field concentrator with an opening for the metal to be shaped, which part it envelops. The magnetic field concentrator is a copper or aluminum cylinder that is slit singly or doubly in a radial manner and that receives the narrowest point of the metal part to be shaped in the opening.
Such magnetic field concentrators are awkward to handle and work with considerable transmission losses because a large part of the pulse energy is lost due to the transfer of said energy first of all to the magnetic field concentrator and then, from the latter, to the metal part to be shaped.